1. Field of the Invention
The invention relates to a manually positionable support device, especially for a work surface. The support device is movable to a desired position and held there for use. Such a support device is useful, for example, to position an electronic interface device such as a computer workstation keyboard, monitor, data tablet or the like, or simply to provide a useful surface for writing, storage or other purposes.
According to the invention, a universal joint support arm is provided with a manual control that is operated temporarily to release rotational engagement between a plurality of coupled joint elements, permitting the support to be repositioned with various degrees of freedom. The joint elements can have axially displaceable rotational engagement surfaces for a plurality of axes of rotation. Tension normally holds the rotational engagement surfaces in axial abutment, preventing relative rotation of the joint elements. The tension is changed, e.g., released temporarily by a control lever coupled to a cable traversing the joint elements, to allow the joints to disengage for repositioning the support arm. According to one embodiment, a positive locking mechanism for the cable rigidly fixes the support device at the chosen position when the control lever is released, by a lever arrangement that isolates the cable from spring tension when locked. According to another embodiment the support arm can have a plurality of elongated connecting arms coupled by such joint elements, dimensioned to permit positioning as appropriate for a user who either sits or stands.
2. Prior Art
It is important in a work environment to enable a worker to adapt the environment to his or her individual needs, including by positioning work surfaces or supported devices at a height, distance and orientation desired to best complement the worker's dimensions and preferences. It is also advantageous for reasons of comfort and to minimize repetitive motion injuries, to enable such position and/or orientation aspects to be changed readily and conveniently, and thus avoid the need to work for a long time in one position or at one precise location. The worker may desire to change any or all of the positioning aspects of the support from time to time.
Various repositionable structures have been developed for making adjustments in the height, extension, lateral position, orientation and other positional aspects of a support surface relative to a base such as a desk, supporting pedestal, mobile foundation device or other structure. Repositionable structures are useful as supports for electronic interface devices such as keyboards, display monitors, data pads, mouses or other pointers, and also for desks, drafting tables, ready-access storage bins, etc. As appropriate, the structures may be configured for the specific use, e.g., with wrist supports for a keyboard, or with clamps for holding down the supported device. Typically, the structures have a plurality of arm members that are coupled so as to be relatively movable by sliding or relative rotation.
The supported device normally must remain secure and stationary against forces produced when the device is positioned at the desired location. Flexible arm members thus are undesirable, particularly for supporting devices such as keyboards, which must be supported against forces produced by the manual activities of the user. However, in the case of a keyboard, the primary force to be resisted is the weight of the user's hands and the force of finger motions. Two or more rigid members typically are coupled in an articulated manner, and means are provided to lock the articulated members relative to one another against expected forces. It is possible to include springs in such supports for bearing part of the weight on the support when the locking means is released, and thus to make the support lighter when it is repositioned. It is also possible to combine some joints that lock and others that do not.
The typical form of locking mechanism for articulated members is frictional. For example, as in U.S. Pat. No. 4,431,329--Baitella, in a rotational joint having axially abutting plates attached to the respective arm members, a threaded tightening bolt with a lever handle can be used to controllably urge the plates into frictional engagement. A pivoting lever can be used instead of a bolt and lever to exert axial pressure, for example as in U.S. Pat. No. 4,976,407--Schwartz et al. Another alternative for a rotational joint is to use a bolt and lever handle or the like circumferentially to shorten a split or C-shaped collar, as in U.S. Pat. No. 4,964,748--McFadden, thereby exerting radial rather than axial pressure for frictional engagement. Each of these alternatives provides a rigid connection if the frictional engagement is tight enough.
There are several drawbacks to known frictional locking mechanisms. If two or more rotational joints each require a frictional adjustment, each rotational coupling must be arranged to lock individually and typically independently of the other rotational couplings, which is cumbersome. In the above McFadden patent, two adjacent joints on the opposite ends of an arm can be tightened or loosened simultaneously using a double-ended tightening arrangement, but only in one rotational axis per joint. For a series of rotational joints between articulated members proceeding from a proximal or fixed end to a distal end carrying a work surface, especially a series of joints having non-parallel rotation axes, repositioning the work surface at the distal end may require numerous steps. A given rotational joint is loosened after envisioning the positioning effect of this rotational joint on the eventual position of the distal end, then the associated articulated member is moved and the joint is re-tightened. Proceeding, for example, from the proximal end to the distal end, attention is required at each rotation axis of each joint.
A universal joint arrangement for a support wherein two or more universal joints are provided between a supporting structure such as a desk and a support platform for a keyboard or the like would advantageously provide a versatile positioning support in that the ultimate position of the support could be arranged at any point in a three dimension span of movement, and at any orientation. Furthermore, the articulated connecting arm members of a support arm comprising universal joints would be subject to various arrangements even while holding the supporting platform at a given position, providing further versatility. However, the need to individually lock each rotation axis of each joint when positioning such a device would be unduly complicated. It is known to provide a universal joint in the form of a ball and socket with an adjustable compression fitting. A ball on one member is affixed in a socket by a collar threaded onto the attached member such that the collar can be tightened to lock the joint frictionally. This is a form of single control applicable to three axes of freedom, but also requires attention to each of the individual joints.
Users of frictionally fixed support platforms often do not tighten the frictional mechanisms to the point that they are fully rigid. Instead, the joints are left firm but not so tight as to preclude movement of the platform by exertion of some force. A looser coupling allows repositioning without attention to the lever or other tightening device, but also less securely holds the support platform. In a universal joint configuration, which inherently has many degrees of freedom, the difficulty in obtaining sufficient security of attachment is compounded.
For all these reasons, plural successive universal joints between articulated members are not likely candidates for a keyboard support or the like that a user will want to reposition conveniently and often.